The ultimate objective of the proposed research is the complete determination of the amino acid sequences of the polypeptide chains of the hemocyanin of Limulus polyphemus. This molecule is a large aggregate of 3.3 x 10 to the 6th power daltons which is composed of 48 subunits each of about 70,000 daltons. As such it constitutes an important model system for the study of self assembly. The subunits are of 8 immunologically distinct types that can be isolated as 5 distinct fractions, each of which is necessary for the assembly of the intact molecule. A prerequisite for complete understanding of the structure and its functional properties is the determination of the primary structure. Our first immediate goal is the determination of the sequence of component II which is being analyzed by x-ray crystallography in another laboratory.